great! Was the limitation 64 KB executable code, btw?

WOAH! 8 KB on some AMS?? I would never have expected it to be this low, considering it's a TI-89. On the 83+ the executable code limit is actually 8 KB, except for Flash apps (the reason why almost everyone uses Flash APPS in ASM programming now). Well it's nice it's gonna get removed now.

New version, v0.2.2, today.
Since v0.2.1, besides a couple non-functional changes (renaming the program again and splitting it into two parts), the program gained the experimental ability to shrink AMS 2.08 for 89, so as to gain back the archive memory sector (64 KB) that this version robbed from users. This capability is implemented by moving 322 bytes of data from the end of the OS to a large (~20 KB) unused area at the beginning of the OS

The ZIP now contains binary patches that can be applied directly with xdelta 1.x, xdelta 3.x or bsdiff. These patches have been created with all optimizations turned on, including the hard-coding of the English language, which prevents language localizations from working properly (not that most readers here care, and besides, many in non-English-speaking countries don't use them because they create incompatibilities in TI-BASIC programs).
Optimizing the drawing of the small font + hard-coding the English language makes e.g. the MODE dialog, made up with localizeable strings drawn with the small font, noticeably faster (I'm comparing two 89 HW2 side by side).

Yes, they did, for even less than that
Something between 96 and 100 bytes (can't check precisely at the moment) on AMS 2.08, and about 800 bytes on AMS 2.09. One could think that this was done on purpose, to promote buying the newer models with twice the amount of Flash memory, the V200 and later the 89T. Needless to say, the silliest pessimizations of their crappy toolchain (between others, double and triple swaps) waste more than 1 KB.

322 bytes is the amount of data that can safely be blindly moved from the end of AMS without caring beyond updating absolute references, because this data is exclusively made of bitmaps. Before these bitmaps are stored multiple menus and dialogs, some of which need to be moved as well to shrink AMS 2.09 by ~500 additional bytes. Menus and dialogs require more checking than the bitmaps did, though they ought to be self-contained as well.
As I wrote in the readme, "my" (Romain's) S-0703F 89 HW2 is now running the shrunk, unlocked AMS 2.08... and the MEM screen shows "Flash ROM free 720876" (of which 64K are, in fact, not available to the user, as shown by the output of getConfg()), just as it does for a fresh AMS 2.03 or 2.05.

I've just uploaded a new version, which shrinks AMS 2.09 for 89 as well
WARNING WARNING WARNING: only lightly tested - I'll go to bed now, that's why

Well, you can always test the modifications to those OS versions on your Titanium. But indeed, not AMS 2.09, which doesn't support the new hardware in HW3/HW4 models (so booting 2.09 on a 89T may leave the calculator in an improper state).
The calculator would refuse 89 OS anyway, unless someone makes the extra step of signing them with the 89T OS key, or installs them "forcefully" (TIB-Receiver if it works on HW3/HW4, or FreeFlash).

Well, what about using the pre-made binary diffs ?